Microglandular adenosis: a prime suspect in triple‐negative breast cancer development

Microglandular adenosis (MGA) and atypical MGA (AMGA) are unusual lesions of the breast. They were once regarded as benign proliferative lesions and innocent bystanders. Several lines of evidence suggested that they could be neoplastic, clonal lesions and a non‐obligate precursor for triple‐negative breast cancers (TNBC). Recent work published in The Journal of Pathology by Guerini‐Rocco and colleagues provided further evidence regarding the precursor–product relationship between MGA/AMGA and TNBC. Using a massively parallel sequencing approach, they demonstrated that MGA/AMGA, particularly those associated with TNBC, could be clonal neoplastic lesions showing clonal non‐synonymous mutations, but none in pure MGA. Importantly, those alterations were observed in the associated TNBC. They were also able to identify recurrent alterations in TP53 in those MGA/AMGA cases as well as their associated TNBC. The findings, in conjunction with others, underscore the significance for MGA in clinical diagnosis. The potential of a benign lesion to progress into an aggressive malignant tumour implies that modification of the current management approach may be necessary. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

The repertoire of somatic genetic alterations of acinic cell carcinomas of the breast: an exploratory,hypothesis‐generating study

Acinic cell carcinoma (ACC) of the breast is a rare form of triple‐negative (that is, oestrogen receptor‐negative, progesterone receptor‐negative, HER2‐negative) salivary gland‐type tumour displaying serous acinar differentiation. Despite its triple‐negative phenotype, breast ACCs are reported to have an indolent clinical behaviour. Here, we sought to define whether ACCs have a mutational repertoire distinct from that of other triple‐negative breast cancers (TNBCs). DNA was extracted from microdissected formalin‐fixed, paraffin‐embedded sections of tumour and normal tissue from two pure and six mixed breast ACCs. Each tumour component of the mixed cases was microdissected separately. Tumour and normal samples were subjected to targeted capture massively parallel sequencing targeting all exons of 254 genes, including genes most frequently mutated in breast cancer and related to DNA repair. Selected somatic mutations were validated by targeted amplicon resequencing and Sanger sequencing. Akin to other forms of TNBC, the most frequently mutated gene found in breast ACCs was TP53 (one pure and six mixed cases). Additional somatic mutations affecting breast cancer‐related genes found in ACCs included PIK3CA, MTOR, CTNNB1, BRCA1, ERBB4, ERBB3, INPP4B, and FGFR2. Copy number alteration analysis revealed complex patterns of gains and losses similar to those of common forms of TNBCs. Of the mixed cases analysed, identical somatic mutations were found in the acinic and the high‐grade non‐acinic components in two out of four cases analysed, providing evidence of their clonal relatedness. In conclusion, breast ACCs display the hallmark somatic genetic alterations found in high‐grade forms of TNBC, including complex patterns of gene copy number alterations and recurrent TP53 mutations. Furthermore, we provide circumstantial genetic evidence to suggest that ACCs may constitute the substrate for the development of more aggressive forms of triple‐negative disease. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Concurrent DNA Copy‐Number Alterations and Mutations in Genes Related to Maintenance of Genome Stability in Uninvolved Mammary Glandular Tissue from Breast Cancer Patients

Somatic mosaicism for DNA copy‐number alterations (SMC‐CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC‐CNAs can undergo clonal expansion, it has been proposed that SMC‐CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array‐based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC‐CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC‐CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC‐CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co‐occurrence of gross SMC‐CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.     

Prevalence of BRCA1/2 large genomic rearrangements in Chinese women with sporadic triple‐negative or familial breast cancer

The prevalence of BRCA1/2 large genomic rearrangements (LGRs) and their underlying mechanisms have not been fully evaluated in Chinese women with breast cancer. In this study, we determined the prevalence of BRCA1/2 LGRs in 834 patients with familial breast cancer (FBC) and 660 patients with sporadic triple‐negative breast cancer (TNBC) who were negative for BRCA1/2 small‐range mutations using the multiplex ligation‐dependent probe amplification method. We found that 20 index patients (2.4%) in the FBC group carried a BRCA1 or BRCA2 LGR, and the frequencies of BRCA1 and BRCA2 LGRs were 1.6% and 0.8%, respectively. Seven index patients (1.1%) carried a BRCA1 LGR in 660 sporadic TNBC patients, whereas no BRCA2 LGRs were found in these patients. Among the BRCA1/2 LGRs, 48.1% (13/27) were novel, and the breakpoints of the majority of the LGRs were identified. ΨBRCA1‐mediated homologous recombination (HR) and Alu‐mediated HR/non‐homologous end‐joining (NHEJ) accounted for 40% and 30% of the BRCA1 LGRs, respectively. Alu‐mediated HR accounted for 71.4% of the BRCA2 LGRs, and the remaining one‐third was generated through Long interspersed nuclear elements (LINE)‐mediated NHEJ. Our findings suggest that both FBC patients and sporadic TNBC patients should be tested for BRCA1/2 LGRs.     

Frequent incidence of BARD1‐truncating mutations in germline DNA from triple‐negative breast cancer patients

Triple‐negative breast cancer (TNBC) accounts for 10–20% of all breast cancers (BCs), and conventional chemotherapy is the only effective systemic treatment. Germline BRCA1/2 mutations are found in approximately 15% of TNBC patients. In the past, we have documented pathogenic mutations in BARD1, a BRCA1 interacting protein, in families at high risk for BC. In this study, we have analyzed germline DNA from 61 estrogen receptor negative patients (of which 42 were TNBC) for the presence of mutations in the BRCA1, BRCA2 and BARD1 gene. BRCA1/2 mutations were found in 8 out of 42 (19%) TNBC patients, but not in the ER?/HER2+ cohort. We also found four good candidate pathogenic BARD1 mutations in the TNBC cohort, including two protein‐truncating mutations (p.Gln564Ter and p.Arg641Ter). Our data suggest that TNBC patients are enriched for pathogenic BARD1 germline mutations as compared to control samples and high BC risk families. Ten of the 42 investigated TNBC patients carry a BRCA pathway mutation (in BRCA1, BRCA2 or BARD1) rendering them susceptible to homologous recombination deficiency. These patients should become eligible for exploring the efficacy of poly (ADP‐ribose) polymerase (PARP) inhibitors.     

Microglandular adenosis or microglandular adenoma? A molecular genetic analysis of a case associated with atypia and invasive carcinoma

Aims: Microglandular adenosis (MGA) is a rare breast lesion, which has long been considered to be hyperplastic. However, atypical forms of MGA (AMGA) and invasive carcinomas arising in the background of MGA are recorded. Recent studies have suggested that MGA may be a non‐obligate precursor of invasive carcinomas that are negative for hormone receptors and lack HER‐2 overexpression (triple‐negative phenotype). The aim of this study was to determine whether MGA is clonal and whether it harbours chromosomal aberrations similar to those found in matched invasive ductal carcinoma of no special type (IDC‐NST). Methods and results: We report on a case comprising MGA, AMGA and a high‐grade IDC‐NST. The three components were separately microdissected and subjected to genetic analysis with high‐resolution microarray comparative genomic hybridisation. Identical genetic changes were detected in all components with subsequent acquisition of additional genetic aberrations in the invasive component, suggesting that MGA was the substrate for the development of the invasive carcinoma. Immunohistochemistry revealed concordant profiles across all components, characterized by triple‐negative phenotype and variable positivity for basal markers. Conclusions: Similar to adenomas, MGA is, at least in some cases, a clonal lesion and may be a non‐obligate precursor of a subgroup of high‐grade triple‐negative and basal‐like breast carcinomas.     

Angiopoietin‐2 mediates blood–brain barrier impairment and colonization of triple‐negative breast cancer cells in brain

Although the incidence of breast cancer metastasis (BCM) in brain has increased significantly in triple‐negative breast cancer (TNBC), the mechanisms remain elusive. Using in vivo mouse models for BCM in brain, we observed that TNBC cells crossed the blood–brain barrier (BBB), lodged in the brain microvasculature and remained adjacent to brain microvascular endothelial cells (BMECs). Breaching of the BBB in vivo by TNBCs resulted in increased BBB permeability and changes in ZO‐1 and claudin‐5 tight junction (TJ) protein structures. Angiopoietin‐2 expression was elevated in BMECs and was correlated with BBB disruption. Secreted Ang‐2 impaired TJ structures and increased BBB permeability. Treatment of mice with the neutralizing Ang‐2 peptibody trebananib prevented changes in the BBB integrity and BMEC destabilization, resulting in inhibition of TNBC colonization in brain. Thus, Ang‐2 is involved in initial steps of brain metastasis cascade, and inhibitors for Ang‐2 may serve as potential therapeutics for brain metastasis. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Young‐aged woman with invasive ductal carcinoma arising in atypical microglandular adenosis: A case report

Microglandular adenosis (MGA) and atypical microglandular adenosis (AMGA) are extremely rare and unique forms of adenosis of the breast. Both forms of adenosis are strongly associated with carcinoma arising in microglandular adenosis (MGACA) and are recognised as precursor lesions of invasive breast carcinoma. Here we provide a clinical report of a young Taiwanese woman who was diagnosed with MGACA and AMGA by means of echo‐guided core biopsy. The subsequent lumpectomy revealed a spectrum of lesions ranging from MGA and AMGA to ductal carcinoma in situ (DCIS) and invasive carcinoma. All of the above lesions have similar immunohistochemical results (expression of S‐100 protein, the absence of oestrogen receptors, progesterone receptors and Her2/neu, and the lack of p63 and the smooth muscle myosin‐heavy chain) with a rather different Ki‐67 labelling proliferation index. This report is of practical interest because the diagnosis of AMGA and MGACA had already been made via needle biopsy.     

RNA-seq analysis identified hormone-related genes associated with prognosis of triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer that currently lacks effective biomarkers and therapeutic targets required to investigate the diagnosis and treatment of TNBC. Here we performed a comprehensive differential analysis of 165 TNBC samples by integrating RNA-seq data of breast tumor tissues and adjacent normal tissues from both our cohort and The Cancer Genome Atlas (TCGA). Pathway enrichment analysis was conducted to evaluate the biological function of TNBC-specific expressed genes. Further multivariate Cox proportional hazard regression was performed to evaluate the effect of these genes on TNBC prognosis. In this report, we identified a total of 148 TNBC-specific expressed genes that were primarily enriched in mammary gland morphogenesis and hormone levels related pathways, suggesting that mammary gland morphogenesis might play a unique role in TNBC patients differing from other breast cancer types. Further survival analysis revealed that nine genes (FSIP1, ADCY5, FSD1, HMSD, CMTM5, AFF3, CYP2A7, ATP1A2, and C11orf86) were significantly associated with the prognosis of TNBC patients, while three of them (ADCY5, CYP2A7, and ATP1A2) were involved in the hormone-related pathways. These findings indicated the vital role of the hormone-related genes in TNBC tumorigenesis and may provide some independent prognostic markers as well as novel therapeutic targets for TNBC.     

The iron chelator deferasirox synergises with chemotherapy to treat triple‐negative breast cancers

To ensure their high proliferation rate, tumor cells have an iron metabolic disorder causing them to have increased iron needs, making them more susceptible to iron deprivation. This vulnerability could be a therapeutic target. In breast cancers, the development of new therapeutic approaches is urgently needed for patients with triple‐negative tumors, which frequently relapse after chemotherapy and suffer from a lack of targeted therapies. In this study, we demonstrated that deferasirox (DFX) synergises with standard chemotherapeutic agents such as doxorubicin, cisplatin and carboplatin to inhibit cell proliferation and induce apoptosis and autophagy in triple‐negative breast cancer (TNBC) cells. Moreover, the combination of DFX with doxorubicin and cyclophosphamide delayed recurrences in breast cancer patient‐derived xenografts without increasing the side‐effects of chemotherapies alone or altering the global iron storage of mice. Antitumor synergy of DFX and doxorubicin seems to involve downregulation of the phosphoinositide 3‐kinase and nuclear factor‐κB pathways. Iron deprivation in combination with chemotherapy could thus help to improve the effectiveness of chemotherapy in TNBC patients without increasing toxicity. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Insulin growth factor receptor‐1 expression and loss of PTEN protein predict early recurrence in triple‐negative breast cancer

Iqbal J, Thike A A, Cheok P Y, Tse G M‐K & Tan P H
(2012) Histopathology  61, 652–659 Insulin growth factor receptor‐1 expression and loss of PTEN protein predict early recurrence in triple‐negative breast cancer Aims: Insulin‐like growth factor receptor‐1 (IGFR‐1) and its signalling axis promote tumorigenesis, metastasis, and resistance to existing forms of cancer therapy, and have become a major focus for the development of anticancer drugs. As oncological management options for triple‐negative breast cancers (TNBCs) are limited, there is potential for the rapid development of novel selective anticancer agents specifically targeting components of the PTEN–phosphoinositide 3‐kinase–AKT pathway, including the phosphorylated form of AKT (pAKT) and the tumour suppressor molecule PTEN. The aim of this study was to conduct immunohistochemical analyses to examine the levels of PTEN, IGFR‐1 and pAKT expression in TNBCs, and determine whether these levels correlated with poor prognosis in this subset of aggressive breast cancers. Methods and results: Immunohistochemistry was performed on paraffin‐embedded tumour tissues from a consecutive cohort of 144 female patients diagnosed with TNBC. Associations of IGFR‐1, PTEN and pAKT expression with clinicopathological parameters, disease‐free survival (DFS) and overall survival (OS) were evaluated. There were significant increases in IGFR‐1 expression (99%) and pAKT expression (92%) with concomitant loss of PTEN expression in the majority of cases (63%). Increased IGFR‐1 expression and loss of PTEN expression were associated with reduced OS and DFS, respectively. pAKT expression showed a strong correlation with basal‐like expression. Combinatorial immunophenotypic analyses showed that loss of PTEN expression with concomitant IGFR‐1 expression correlated with poor DFS. Conclusions: A high percentage of PTEN loss with overexpression of IGFR‐1 and pAKT in TNBC indicates the potential of these molecules for predicting early recurrence and/or as targets in the formulation of effective alternative therapy regimens.     

Germline mutations in DNA repair genes may predict neoadjuvant therapy response in triple negative breast patients

Triple negative breast cancers (TNBCs) represent about 15–20% of all breast cancer cases and are characterized by a complex molecular heterogeneity. Some TNBCs exhibit clinical and pathological properties similar to BRCA‐mutated tumors, without actually bearing a mutation in BRCA genes. This “BRCAness” phenotype may be explained by germline mutations in other genes involved in DNA repair. Although respond to chemotherapy with alkylating agents, they have a high risk of recurrence and progression. Some studies have shown the efficacy of neoadjuvant therapy in TNBC patients with DNA repair defects, but proper biomarkers of DNA repair deficiency are still needed. Here, we investigated if mutations in DNA repair genes may be correlated with anthracyclines/taxanes neoadjuvant therapy response. DNA from 19 TNBC patients undergoing neoadjuvant therapy were subjected to next generation sequencing of a panel of 24 genes in DNA repair and breast cancer predisposition. In this study, 5 of 19 patients (26%) carried a pathogenic mutation in BRCA1, PALB2, RAD51C and two patients carried a probable pathogenic missense variant. Moreover, VUS (Variants of Unknown Significance) in other genes, predicted to be deleterious by in silico tools, were detected in five patients. Germline mutations in DNA repair genes were found to be associated with the group of TNBC patients who responded to therapy. We conclude that a subgroup of TNBC patients have defects in DNA repair genes, other than BRCA1, and such patients respond favourably to neoadjuvant anthracyclines/taxanes therapy. © 2016 Wiley Periodicals, Inc.     

Intraindividual genomic heterogeneity of high‐grade serous carcinoma of the ovary and clinical utility of ascitic cancer cells for mutation profiling

Intraindividual tumoural heterogeneity (ITH) is a hallmark of solid tumours and impedes accurate genomic diagnosis and selection of proper therapy. The aim of this study was to identify ITH of ovarian high‐grade serous carcinomas (OSCs) and to determine the utility of ascitic cancer cells as a resource for mutation profiling in spite of ITH. We performed whole‐exome sequencing, copy number profiling and DNA methylation profiling of four OSC genomes by using multiregional biopsies from 13 intraovarian lesions, 12 extraovarian tumour lesions (omentum/peritoneum), and ascitic cells. We observed substantial levels of heterogeneity in mutations and copy number alterations (CNAs) of the OSCs. We categorized the mutations into ‘common’, ‘shared’ and ‘private’ according to the regional distribution. Six common, eight shared and 24 private mutations were observed in known cancer‐related genes. Common mutations had a higher mutant allele frequency, and included TP53 mutations in all four OSCs. Region‐specific chromosomal amplifications and deletions involving BRCA1, PIK3CA and RB1 were also identified. It is of note that the mutations detected in ascitic cancer cells represented 92.3–100% of overall somatic mutations in the given case. Phylogenetic analyses of ascitic genomes predicted a polyseeding origin of somatic mutations in ascitic cells. Our results demonstrate that, despite ITH, somatic mutations, CNAs and DNA methylations in both ‘common’ category and cancer‐related genes were highly conserved in ascitic cells of OSCs, highlighting the clinical relevance of genome analysis of ascitic cells. Ascitic tumour cells may serve as a potential resource for discovering somatic mutations of primary OSC with diagnostic and therapeutic relevance. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Gross cystic disease fluid protein‐15 and mammaglobin A expression determined by immunohistochemistry is of limited utility in triple‐negative breast cancer

Aims: In addition to oestrogen and progesterone receptors, gross cystic disease fluid protein‐15 (GCDFP‐15) and mammaglobin A (MAM) are the most common markers used to identify breast origin by immunohistochemistry. GCDFP‐15 expression has been reported in approximately 60% of breast carcinomas and MAM expression in approximately 80%. Data on their expression in triple‐negative breast cancer (TNBC) are very limited. The aim of this study was to examine the expression of these markers in TNBC to determine their utility in pathological diagnosis. Methods and results: We studied the immunohistochemical (IHC) expression of GCDFP‐15 and MAM in 63 primary and 118 metastatic TNBCs. GCDFP‐15 staining was present in 14% of primary and 21% of metastatic TNBCs. MAM staining was present in 25% of primary and 41% of metastatic TNBCs. The frequency of expression of GCDFP‐15 and/or MAM was 30% in primary and 43% in metastatic TNBCs, and many positive tumours had only focal staining. Conclusions: Staining for GCDFP‐15 and/or MAM in triple‐negative carcinomas helps to confirm breast origin, but most tumours in this subgroup of breast carcinomas lack expression of either marker.     

Cytokeratin 7: a re‐evaluation of the ‘tried and true’ in triple‐negative breast cancers

Davion S M, Siziopikou K P & Sullivan M E
(2012) Histopathology  61, 660–666 Cytokeratin 7: a re‐evaluation of the ‘tried and true’ in triple‐negative breast cancers Aims: Triple‐negative breast cancers (TNBCs) are often poorly differentiated tumours that can present clinically as metastases of an unknown primary. Immunohistochemical panels are frequently used to determine the likelihood of a breast primary, but in this tumour subset cytokeratin (CK)7 may be the only positive finding. In this study we aimed to evaluate a commonly employed immunohistochemical panel using a large group of TNBCs (both basal‐like and unclassified), and to analyse the CK7 staining patterns. Methods and results: Tissue microarrays containing 138 TNBCs were stained with antibodies against CK7, CK20, gross cystic disease fluid protein 15 (GCDFP‐15), and mammaglobin. CK5/6 staining was used to identify basal‐like tumours. CK7 staining was notably heterogeneous, with 14.5% of all cases demonstrating ≤20% tumour cell staining. A greater proportion of basal‐like TNBCs than of unclassified TNBCs showed focal staining. GCDFP‐15 and mammaglobin were not expressed in the majority of TNBCs, and were less frequently positive in basal‐like than in unclassified TNBCs. Conclusions: TNBCs are commonly negative for most immunomarkers indicative of breast origin, with the exception of CK7. As about one in five TNBCs showed only focal CK7 positivity, use of this marker must be interpreted with caution, especially in small samples, so that the possibility of a breast primary is not overlooked.     

MRI reveals increased tumorigenesis following high fat feeding in a mouse model of triple‐negative breast cancer

High animal fat consumption is associated with an increase in triple‐negative breast cancer (TNBC) risk. Based on previous MRI studies demonstrating the feasibility of detecting very early non‐palpable mammary cancers in simian virus 40 large T antigen (SV40TAg) mice, we examined the effect of dietary fat fed from weaning to young adulthood in this model of TNBC. Virgin female C3(1)SV40TAg mice (n = 16) were weaned at 3–4 weeks of age and then fed either a low fat diet (LFD) (n = 8, 3.7 kcal/g; 17.2% kcal from vegetable oil) or a high animal fat diet (HAFD) (n = 8, 5.3 kcal/g; 60% kcal from lard). After 8 weeks on the diet (12 weeks of age), fast spin echo MR images of inguinal mammary glands were acquired at 9.4 T. Following in vivo MRI, mice were sacrificed and inguinal mammary glands were excised and formalin fixed for ex vivo MRI. 3D volume‐rendered MR images were then correlated with mammary gland histology to assess the glandular parenchyma and tumor burden. Using in vivo MRI, an average of 3.88 ± 1.03 tumors were detected per HAFD‐fed mouse compared with an average of 1.25 ± 1.16 per LFD‐fed mouse (p < 0.007). Additionally, the average tumor volume was significantly higher following HAFD feeding (0.53 ± 0.45 mm³) compared with LFD feeding (0.20 ± 0.08 mm³, p < 0.02). Analysis of ex vivo MR and histology images demonstrated that HAFD mouse mammary glands had denser parenchyma, irregular and enlarged ducts, dilated blood vessels, increased white adipose tissue, and increased tumor invasion. MRI and histological studies of the SV40TAg mice demonstrated that HAFD feeding also resulted in higher cancer incidence and larger mammary tumors. Unlike other imaging methods for assessing environmental effects on mammary cancer growth, MRI allows routine serial measurements and reliable detection of small cancers as well as accurate tumor volume measurements and assessment of the three‐dimensional distribution of tumors over time.     

Comprehensive genetic features of gastric mixed adenoneuroendocrine carcinomas and pure neuroendocrine carcinomas

We aimed to determine the pathogenesis of gastric mixed adenoneuroendocrine carcinoma (MANEC) and pure neuroendocrine carcinoma (NEC), which is largely unknown. Targeted DNA sequencing was performed on 34 tumor samples from 21 patients – 13 adenocarcinoma (ADC)/NEC components from MANECs and eight pure NECs – and 21 matched non‐neoplastic gastric tissues. Mutational profiles of MANECs/NECs were compared with those of other tumors using public databases. The majority (64.1%; 59/92) of mutations in MANEC were shared by both ADC and NEC components. TP53 was the most commonly mutated gene in MANEC (69.2%, 9/13) and pure NEC (87.5%, 8/9). All TP53 mutations in MANEC were pathogenic mutations and were shared by both ADC and NEC components. A subset of TP53^WT MANECs had a microsatellite‐unstable phenotype or amplifications in various oncogenes including ERBB2 and NMYC, and the only TP53^WT pure NEC harbored MYC amplification. Compared to NEC in other organs, NECs arising from the stomach had unique features including less frequent RB1 mutations. Differentially altered genes of MANEC ADC components were significantly associated with receptor tyrosine kinase signaling pathways, while differentially altered genes of MANEC NEC components were significantly associated with the NOTCH signaling pathway. Our data provide evidence suggesting a possible clonal origin of ADC and NEC components of MANEC, and we found that gastric MANECs and pure NECs are distinct entities with unique mutational profiles and underlying protein networks. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

NFIB promotes cell survival by directly suppressing p21 transcription in TP53-mutated triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with limited treatment options and poor prognosis. There is an urgent need to identify and understand the key factors and signalling pathways driving TNBC tumour progression, relapse, and treatment resistance. In this study, we report that gene copy numbers and expression levels of nuclear factor IB (NFIB), a recently identified oncogene in small cell lung cancer, are preferentially increased in TNBC compared to other breast cancer subtypes. Furthermore, increased levels of NFIB are significantly associated with high tumour grade, poor prognosis, and reduced chemotherapy response. Concurrent TP53 mutations and NFIB overexpression (z-scores > 0) were observed in 77.9% of TNBCs, in contrast to 28.5% in non-TNBCs. Depletion of NFIB in TP53-mutated TNBC cell lines promotes cell death, cell cycle arrest, and enhances sensitivity to docetaxel, a first-line chemotherapeutic drug in breast cancer treatment. Importantly, these alterations in growth properties were accompanied by induction of CDKN1A, the gene encoding p21, a downstream effector of p53. We show that NFIB directly interacts with the CDKN1A promoter in TNBC cells. Furthermore, knockdown of combined p21 and NFIB reverses the docetaxel-induced cell growth inhibition observed upon NFIB knockdown, indicating that NFIB's effect on chemotherapeutic drug response is mediated through p21. Our results indicate that NFIB is an important TNBC factor that drives tumour cell growth and drug resistance, leading to poor clinical outcomes. Thus, targeting NFIB in TP53-mutated TNBC may reverse oncogenic properties associated with mutant p53 by restoring p21 activity. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.